Toward device-quality GaAs growth by molecular beam epitaxy on offcut Ge/Si1−xGex/Si substrates

Abstract

Growth kinetics and modeling of selective molecular beam epitaxial growth of GaAs ridge quantum wires on prepatterned nonplanar substrates Molecular beam epitaxial growth of InAs/AlGaAsSb deep quantum well structures on GaAs substratesThe epitaxial growth of GaAs on Si substrates through the use of a Ge/graded Si 1Ϫx Ge x /Si buffer layer would allow monolithic integration of GaAs-based opto-electronics with Si microelectronics. As an initial step toward this goal, this study examines factors which influence the quality of GaAs growth by molecular beam epitaxy ͑MBE͒ on bulk Ge substrates. Key findings include the need for an epitaxial Ge smoothing cap deposited in the MBE chamber, the significant detrimental effect of As overpressure on the resultant GaAs crystalline quality, and the efficiency of a very thin (ϳ3 nm) migration enhanced epitaxy ͑MEE͒ nucleation layer at suppressing both anti-phase domain ͑APD͒ formation and interdiffusion across the GaAs/Ge heterointerface. Using this developed optimized growth process, APD-free GaAs on Ge is obtained which has undetectable Ga and Ge cross-diffusion, and As diffusion into the substrate at р1ϫ10 18 cm Ϫ3 . Preliminary results for growths on Ge/Si 1Ϫx Ge x /Si substrates are also presented.

Structure of Ge(113): Origin and Stability of Surface Self-Interstitials

“…High-index surfaces are of increasing interest as substrates for electronic device applications. Their inherent structural anisotropy reduces antiphase domain formation, threading dislocation pileup, and surface roughness during heteroepitaxy, leading to improved epitaxial layers and novel electronic properties [1][2][3]. Of the few highindex Si and Ge surfaces with stable planar reconstructions [4], the (113) orientation, about midway between (001) and (111), is particularly interesting.…”

III-V Device Integration on Silicon Via Metamorphic SiGe Substrates

“…III-V growth was subsequently initiated by MBE using methods previously demonstrated to control nucleation of the III-V/Ge interface, enabling elimination of anti-phase domains and cross-diffusion of Ga, As and Ge to below SIMS detection limits for a GaAs nucleation layer of less than 100nm (2). For all GaAs/SiGe/Si epi structures discussed here, GaAs nucleation was completed by MBE using this method and capped with 100nm of GaAs grown at 500 o C as described elsewhere (3,4). Following this initial nucleation, either MBE or MOCVD was used to grow the devices as indicated in the following sections.…”

“…The AM0 efficiency for the same cell shown in figure 4(a) was 15.5% with a V oc of 980 mV, and is also the highest independently verified efficiency and V oc reported to date under this spectrum (17). The high performance obtained, in spite of the large lattice mismatch (4%) between the fully relaxed GaAs cell and the Si substrate, is attributed to the achievement of a high V oc , 973 mV, which is the consequence of maintaining a low TDD value of ~ 1x10 6 cm -2 while simultaneously eliminating other mismatch related defects such as anti-phase domains and auto-doping, which could otherwise lower V oc (2,3 18 (a) (b) Figure 3. (a) SJ GaAs p+/ and (b) DJ InGaP/GaAs p+/n solar cell structures on SiGe.…”

III–V Multijunction Solar Cell Integration with Silicon: Present Status, Challenges and Future Outlook

“…For the III-V solar cell growth, an initial epitaxial Ge layer was grown by MBE followed by the growth of GaAs on Ge at an initial low growth temperature using migration-enhanced epitaxy, details of which can be found in Refs Sieg et al 1998). This process has been shown to suppress the formation of APDs due to the controlled nucleation at the GaAs/Ge interface, and etch-pit density of 5 Â 10 5 -2 Â 10 6 cm −2 was reported for the GaAs layers grown on virtual Ge substrate (Sieg et al 1998).…”